Arrangement for fastening a piston-cylinder arrangement and method for replacing sealings therein

ABSTRACT

A mounting apparatus for a piston-cylinder arrangement ( 10,11 ) in a derrick ( 1 ) placed on a drill floor ( 2 ), which hydraulic piston-cylinder arrangement ( 10,11 ) is adapted to raise and lower a yoke ( 8 ) which travels on guide rails ( 7 ) in the derrick ( 1 ) itself, where the cylinder ( 20 ) is firmly held by a mounting apparatus ( 31 ) in relation to the drill floor ( 2 ). For the changing of gaskets ( 27 ) on the piston ( 21 ) and the cylinder ( 20 ), the cylinder is arranged so as to be lowerable in relation to the mounting thereof. The mounting apparatus ( 31 ) is designed to be releasable and comprises a flange ( 32 ) permanently mounted on the cylinder ( 20 ), a fixing device ( 37 ) in fixed position in relation to drill floor ( 2 ), a dividable locking ring ( 34 ), and a locking device ( 32 ) and the fixing device ( 37 ) and being firmly held in engagement with the aid of the locking device ( 38 ). A method of changing gaskets on a piston and cylinder is also described.

The present invention relates to an apparatus for mounting apiston-cylinder arrangement in a derrick, comprising two or morehydraulic piston-cylinder arrangements for raising and lowering a yokewhich travels on guide rails in the derrick itself, and a method ofchanging gaskets in this type of piston-cylinder arrangement.

A derrick structure which was developed in 1987 by the present inventorand which has shown great promise embodies the RamRig™ concept. Twohydraulic piston-cylinder arrangements are used in the derrick forraising and lowering the drill string. The cylinders operate between thedrill floor and a yoke which travels on guide rails in the derrickitself. The advantages of this concept are numerous. Among the mostimportant are that is possible to place the drill floor at a higherlevel than the platform floor, that a derrick may be constructed havinga significantly lower air resistance, and that a higher level of safetyand longer lifetime are attained for the most expensive components ofthe derrick.

Since it is possible to position the drill floor higher than theplatform floor, pipe handling is significantly simplified. There is nolonger any need to arrange the pipe handling equipment at a high levelin the derrick. All pipe handling equipment may be placed on theplatform floor and the drill floor.

U.S. Pat. No. 4,341,373 shows a similar derrick structure, where a yokeis slidably mounted on guide rails and is raised with the aid of aplurality of piston-cylinder arrangements. A travelling block issuspended from the yoke by a plurality of wire lines. In the travellingblock is mounted the top drive.

The object of the present invention is to solve an important practicalproblem in the realization of the RamRig™ concept. This problem consistsof the need to periodically change gaskets on the piston and/or cylinderin the piston-cylinder arrangement. This is very important with respectto safety. By means of the features disclosed in the characterizingclause of the subsequent claim 1, and the method disclosed herein wehave succeeded in providing a simple mounting apparatus for the cylinderwhich permits rapid and uncomplicated changing of the gaskets.

The invention will now be explained in greater detail with reference tothe enclosed drawings, where

FIG. 1 shows a RamRig™ derrick in every essential detail;

FIG. 2 shows the derrick schemaatically, viewed from the side;

FIG. 3 shows the derrick schematically, viewed from the front, with thetop drive in its lowermost position;

FIG. 4 shows the derrick schematically, viewed from the front, with thetop drive in its uppermost position;

FIGS. 5-7 show a section of the derrick and the drill floor andillustrate the lowering of one of the cylinders in sequence; and

FIGS. 8-13 show in detail the apparatus for mounting the cylinder andillustrate in detail the solution for this mounting process.

FIG. 1 shows a derrick 1 positioned on a drill floor. Drill floor 2 isarranged at a higher level than the platform floor 3, enabling the pipehandling equipment 4 to be placed mainly between the platform floor 3and drill floor 2. Derrick 1 is generally gantry-shaped. having gantrylegs 5, 6. Guide rails 7 for a yoke 8 and a top drive 9 run along eachgantry leg 5, 6. Hydraulic piston-cylinder arrangements 10 and 11 arepositioned so as to extend along each gantry leg 5, 6, and operatebetween drill dloor 2 and yoke 8, for moving yoke 8 vertically alongguide rails 7.

The yoke 8 is provided with a plurality of sheaves 12, preferably four,for running the wire lines 13. Wire lines 13 extend from drill floor 2along each gantry leg 5, 6, over sheaves 12 and down to top drive 9. Byretracting and extending the piston-cylinder arrangement 10, 11, it isthereby possible to raise and lower top drive 9.

In FIGS. 2, 3 and 4 the function of the hoisting system is seen mostclearly. In FIGS. 2 and 3 the piston-cylinder arrangement 10, 11 isshown in a completely retracted state. Top drive 9 is then at itslowermost position, quite close to the drill floor. Yoke 8 is at theupper end of the piston-cylinder arrangement.

When the pistons in the piston-cylinder arrangement are extended, yoke 8is lifted along guide rails 7 and up to the top of derrick 1. The topdrive is then lifted, as a result of the transmission generated as wirelines 13 are run over sheaves 12, from its position adjacent drill floor2 to a position directly below yoke 8. The height to which top drive 9is lifted is thus the double of that to which yoke 8 is lifted.

There may, for example, be as many as eight wire lines 13 arranged inthe hoisting apparatus described above, with the wire lines being strungtwo by two in their respective tracks over the same sheave 12. On yoke 8four sheaves are arranged in pairs at each end of yoke 8. Wire lines 13are thus arranged in two sets 13 a and 13 b, extending from attachmentpoints 14 a and 14 b at drill floor 2, over sheaves 12 and down to topdrive 9. Attachment points 14 a and 14 b are spaced apart horizontallyby a distance corresponding approximately to the length of yoke 8.

FIGS. 5-7 provide a schematic illustration of the lower portion ofderrick 1 and drill floor 2. Here are also shown the piston-cylinderarrangements 10, 11, yoke 8 with sheaves 12 and top drive 9. Wire lines13 run from drill floor 2 over their respective sheaves 12 and down totop drive 9.

Each piston-cylinder arrangement 10, 11 consists of a cylinder 20 and apiston 21 having piston rod 22. Cylinder 20 is secured at one endthereof to drill floor 2, while piston rod 22 is attached to yoke 8.Piston 21 divides the cylinder into two chambers, a lower chamber and anupper chamber. The lower chamber is circular-cylindrical and delimitedonly by the walls of cylinder 20 and the lower end surface 25 of thepiston. The upper chamber is also delimited by the walls of cylinder 20,but in addition is bounded by piston rod 22 and the upper annularsurface 26 of piston 21. the piston is further provided with one or moregaskets 27, and the cylinder comprises an end cover (not shown) with agasket (not shown) for sealing off cylinder 20.

Cylinder 20 is suspended in a support column 28 in a suspension device29 at the upper end of support column 28. Feed lines 30 for supplyinghydraulic fluid to cylinder 20 are inserted through an opening in thelower end of the support column. Support column 28 is, on its part,fixed in place with the aid of a mounting apparatus 31 (not shown inFIGS. 5-7) at drill floor 2. This mounting apparatus 31 is illustratedin detail in FIGS. 8-13, which figures show a detailed section at drillfloor 2.

FIGS. 8(a)-8(c) shows cylinder 20 with support column 28 mounted indrill floor 2. FIGS. 8(a), 8(c), 9(a) and 10(a) show a side elevation ofthe mounting apparatus. FIGS. 8(b), 9(b), 9(c), 10(b) and 10(c)illustrate top view of the fixing devic 37 and locking means 38.Mounting apparatus 31 is also shown in an enlarged section in FIG. 8(c),and consists of a flange 32 fixedly joined to support column 28, inwhich flange 32 is formed a groove 33 which extends around the peripheryof support column 28. When the mounting apparatus 31 is in assembledstate, a locking ring 34 is engaged with groove 33. Locking ring 34 alsorests against drill floor 2, either directly or via a structure firmlyconnected with drill floor 2. To permit the attachment and removal oflocking ring 34, the ring 34 is separated into two or more segments.

Radially exterior to locking ring 34 is provided a safety ring 35 whichis also separated into two or more segments. Safety ring 35 is adaptedto hold locking ring 34 in engagement with groove 33 in flange 32, andthus fills out a gap 36 between locking ring 34 and a fixing device 37,which is firmly connected with drill floor 2. To prevent safety ring 35from moving upwards and thus out of gap 36, a locking means 38, alsodivided into two or more sections, is arranged over said ring.

Locking means 38 may be secured to fixing device 37 with the aid of, forexample, a plurality of bolts 39.

With the aid of FIGS. 5-13, the method of changing piston gaskets 27 andthe gasket for cylinder 20 at the upper end thereof will now beexplained. First, yoke 8 is locked securely to its guide rails 7 inderrick 1 so as to relieve the downward-directed force of thepiston-cylinder arrangement 10, 11. Then the mounting apparatus 31 isloosened, first by unscrewing bolts 39 to enable the removal of lockingmeans 38. This results in the situation depicted in FIGS. 9(a)-9(c).FIG. 9(c) illustrates the removed locking means 38. FIGS. 9(a) and 9(b)show a side elevation and top view of the mounting apparatus having thelocking means removed. The fixing device 37 is visible.

Now it is possible to lift safety ring 35 out of gap 36 as shown inFIGS. 10(a)-10(c). The safety ring 35 is illustrated in FIG. 10(c) andthe remainder of the mounting apparatus is illustrated in FIGS. 10(a)and 10(b).

Now the locking ring 34 is exposed. However, it is now clamped betweenthe upper wall of groove 33 and drill floor 2. Cylinder 20 and supportcolumn 28 must thus be raised slightly in order to nullify this clampingeffect. This may be done in a variety of ways. For example, one mayapply a pressure in cylinder 20 on the rod side 26 of piston 21 and,with the aid thereof, raise cylinder 20 and support column 28. Anotherway to do this is to position a jack 40 (see FIG. 6 and FIG. 7), or thelike, between drill floor 2 and a projection 41 on support column 28, orbetween platform floor 3 and support column 28. If desired, another typeof lifting device may be used.

FIGS. 12(a), 12(b) and 12(d) illustrate the situation after locking ring34 has been removed from the mounting apparatus, where locking ring 34is shown in FIG. 12(c). An enlarged section of the remaining part ofmounting apparatus 31 is also shown in FIG. 12(d).

When the mounting apparatus for support column 28 has now been loosened,the support column 28 with cylinder 20 may be lowered downward inrelation to drill floor 2. This lowering may be done, for example, bycontrolled release of the pressure on the top side 26 of piston 21. Saidlowering may be carried out until piston 21 rests against the end coverof cylinder 20. Now the end cover must be removed in order for cylinder20 to be drawn off piston 21. To hold cylinder 20 during the removal ofthe end cover, some form of hoisting or lifting apparatus, for example,a jack 40, must be provided.

After cylinder 20 has been drawn completely off piston 21, the gaskets27 on piston 21 may be changed in a conventional manner. Gaskets in theend cover of cylinder 20 and any gaskets at the upper end of thecylinder may also be changed in a conventional manner.

In remounting of cylinder 20, it is lifted up and drawn down over piston21 with the aid, for example, of jacks 40. Then the end cover may bemounted and pressure may again be applied in cylinder 20 on the upperside 26 of piston 21, whereby with the aid of this hydraulic pressurethe cylinder may be raised upward in relation to drill floor 2 untilgroove 33 in flange 32 aligns with fixing device 37. Locking ring 34 isthen put into place, cylinder 20 with support column 28 is lowereddownward until locking ring 34 rests on drill floor 2, and safety ring35 is positioned in gap 36, thereafter to be securely locked with theaid of locking means 38 and bolts 39. The changing of the gaskets is nowcompleted, and the only task remaining is to release the yoke 8 from itslocked position on the guide rails.

Although a specific embodiment of the mounting apparatus is described inthe above, the present invention is not restricted to the use of thisspecific embodiment. Locking ring 34 may also be held in engagement withgroove 34 in other ways and with the aid of devices other than thoseshown and described herein. During the process, certain steps in themethod may be carried out in a different sequence; for example, one mayremove the cylinder's end cover before commencing the lowering of thecylinder in relation to the drill floor, but then it will not bepossible to utilize hydraulic pressure on the rod side of the piston toexecute a controlled lowering, and one would thus have to use othertypes of hoisting or lifting devices in order to accomplish this.

What is claimed is:
 1. An apparatus for mounting a piston-cylinderarrangement in a derrick (1) placed on a drill floor (2), wherein saidpiston-cylinder arrangement (10, 11) is adapted to raise and lower ayoke (8) which travels on guide rails (7) in the derrick (1), andcomprises a cylinder (20), a piston (21), and a piston rod (22), whereinsaid piston rod (22) is joined at one end thereof to the piston (21),wherein said piston (21) is adapted to be inserted into the cylinder(20), wherein an end of said piston rod (22) opposite the piston (21)being connected to the yoke (8), and the cylinder (20) being heldsecurely with the aid of a mounting apparatus (31) in relation to thedrill floor (2), characterized in that the cylinder (20), for thechanging of gaskets (27) on the piston (21) and the cylinder (20), isarranged so as to be lowerable in relation to the mounting apparatus(31) thereof, and that the mounting apparatus (31) therefor is designedto be releasable and comprises a flange (32) permanently mounted on thecylinder (20), a fixing device (37) in fixed position in relation to thedrill floor (2), a dividable locking ring (34), and a locking means(38), said locking ring (34) being adapted for engagement between theflange (32) and the fixing device (37) and being firmly held inengagement with the aid of the locking means (38).
 2. An apparatus inaccordance with claim 1, characterized in that the locking ring (34) isadapted for placement in engagement with a groove (33) in the flange(32), which groove (33) extends continuously or with interruption arounda substantial portion of the periphery of the cylinder (20), and thatthe locking ring (34) is maintained in said engagement with the aid of adividable safety ring (35) which is placed between the locking ring (34)and the fixing device (37).
 3. An apparatus in accordance with claim 2,characterized in that the locking means (38) constitutes a dividableflange which in mounted state is secured to the fixing device (37) andbears against the safety ring (35) and optionally also the locking ring(34).
 4. An apparatus in accordance with claim 1, 2 or 3, characterizedin that the cylinder (20) is suspended in a support column (28) whichencloses the cylinder (20) and that the flange (32) is attached to thissupport column (28).
 5. A method of changing gaskets in at least onepiston-cylinder arrangement (10,11) in a derrick (1) located on a drillfloor (2), said at least one piston-cylinder arrangement (10,11) beingadapted to raise and lower a yoke (8), which travels on guide rails (7)on the derrick (1), each of said at least one piston-cylinderarrangement (10, 11) comprising a cylinder (20), a piston (21) and apiston rod (22), wherein said piston rod (22) is joined at one endthereof to said piston (21), wherein said piston (21) is adapted to beinserted into said cylinder (20), an end of said piston rod (22)opposite said piston (21) being connected to the yoke (8), and saidcylinder (20) being held securely with the aid of mounting apparatus(31) in relation to the drill floor (2), said method comprising thesteps of: locking the yoke (8) to the derrick; relieving hydraulicpressure within said cylinder (20); exposing a locking device (38);removing a locking ring (34) from engagement with a flange (32) mountedon said cylinder (20); removing an end cover from said cylinder (20);lowering said cylinder (20) in relation to the drill floor (2) and saidpiston rod (22) such that said piston rod (22) is completely drawn outof said piston (21); removing at least one gasket (27) on said piston;replacing said at least one gasket (27) on said piston; raising saidcylinder (20) such that said cylinder (20) is slid back onto piston (21)whereby said flange (32) is aligned with a fixing device (37); mountingthe end cover on said cylinder (20); engaging the locking ring (34)between the flange (32) and the fixing device (37); securing the lockingdevice (38) in place; restoring hydraulic pressure within said cylinder(20); and releasing the yoke (8) from the locked position on the derrick(2).
 6. The method of changing gaskets according to claim 5, furthercomprising the steps of: removing at least one gasket from at least oneof an upper end and the end cover of said cylinder (20); and replacingsaid at least one gasket from at least one of the upper end and the endcover of said cylinder (20).
 7. A method in accordance with claim 5,characterized in that, prior to removal of the end cover for thecylinder (20), pressure is applied in a chamber of the cylinder (20), onthe piston rod side (26) of the piston (21), to effect controlledlowering of the cylinder (20) in relation to the drill floor (2), thatthe end cover is then removed, and that the further lowering andwithdrawal of the cylinder (20) from the piston (21) is carried out withthe aid of a separate hoisting/lifting apparatus.
 8. A method inaccordance with claim 5 or 6, characterized in that the cylinder (20) israised slightly after the locking device (38) is released to nullify anypossible clamping effect between the locking ring (34), a groove (33) inthe flange (32) and the drill floor (2).